Microstructure and mechanical properties of a spark plasma sintered Fe-11Cr-2.3B-6Al-15Mn alloy

A bulk Fe-11Cr-2.3B-6Al-15Mn alloy has been successfully produced using Fe, Cr, Al, Mn and B powders by Mechanical alloying (MA) and Spark plasma sintering (SPS). Alloying behavior, microstructure and phase evolution of the sintered specimen have been investigated by using X-ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is shown that a supersaturated solid solution with body-centered cubic (BCC) structure is formed during MA. After sintering, Fe2AlCr, CrFeB-type boride and Mn2B-type boride precipitate in the γ-Fe matrix, and no network structures are observed. The hardness, three-point bending strength and fracture toughness of the sintered alloy are 54.8 HRC, 2080 MPa and 8.14 MPa/m1/2, respectively. The sintered alloy shows compressive strength of 2553 MPa at room temperature, and especially has high compressive strength of 948 MPa at 600 °C. The high hardness and compressive strength can be attributed to solid solution of Al, Cr and Mn, precipitation of Fe2AlCr, CrFeB and Mn2B in the γ-Fe matrix. The dense nanocrystalline microstructure produced by the combine of MA and SPS can also help improving mechanical properties of the sintered alloy.